Size effects in multi-scale materials processing and manufacturing

Size effects (SEs) exist in many domains, and are caused by changes in the values of parameters of materials, structures, or systems individually or collectively known as size effect factors. SEs induce a variety of scale-dependent behaviours, phenomena, and performances during the multiscale processing and manufacturing of materials, such as the macro-, meso-, and microscale ones examined by the researches described in this paper. Furthermore, the parts and components fabricated from multiscale processing and manufacturing exhibit the scatters of quality and properties. This paper uses multiscale machining and deformation-based manufacturing as the case studies of material processing and manufacturing to review and analyse SEs and their manifestations. The current status of multiscale manufacturing research and its possible future avenues are articulated and discussed, and key problems that must be solved and unknowns that must be understood are highlighted. This paper thus presents a broad understanding and insight into SEs that influence the material processing and manufacturing for making multiscale parts and components. It also examines the bottleneck problems generated by SEs in such processing and manufacturing arena, and how these can be solved to enable the high efficiencies of multi-scale materials processing and manufacturing to be realised. • Size effect (SE) factors and their classification are given. • Manifestations of SEs and the classification into three identified phenomena are articulated. • The SE available mechanisms are summarised and the loopholes are analysed. • The SE-induced behaviour and phenomena are delineated. • SE caused scatters are explicated and the impacts in manufacturing are discussed.